Infant survivors of idiopathic respiratory distress syndrome (RDS) develop pulmonary residua which are believed to predispose these infants to more frequent and/or more severe respiratory infections. To assess this aspect of the long-term morbidity of RDS, we are systematically and prospectively evaluating the frequency, severity, and etiologies of acute respiratory illnesses in survivors of RDS, and preterm infants who did not have RDS compared to normal infants matched for sex, race, season of birth and presence of pre-adolescent children in the household.